Sintered glass containing ferrous material

ABSTRACT

This invention relates to sintered ferrous materials. Sintered ferrous materials in accordance with the invention contain at least 50 percent by weight of iron and glass in an amount of not more than 2 percent by weight. The iron can be present as pure iron or as an alloy thereof. The materials can be produced by known powder metallurgical methods, for example by compression in the presence of a lubricant and subsequent heating. The glass generally serves to seal the pores between the particles of the iron-containing powder, and the materials have been found to have low porosity to gases and liquids and increased corrosion resistance compared with similar materials containing no glass. Sintered ferrous materials in accordance with the invention can be used for producing valve seats.

United States Patent 11 1 Cadle 1 1 SINTERED GLASS CONTAINING FERROUSMATERIAL [75] Inventor: Terence M. Cadle, Coventry.

England [73] Assignee: Bries Engineering Ltd., Coventry.

England [22] Filed: Aug. 31, 1972 [21] App]. No.: 285,120

OTHER PUBLICATIONS Goetzel, C. 0.. Treatise on Powder Metallurgy. Vol.1,

1 June 24, 1975 lnterscience, N.Y., 1949, pp. 689-695, TN 695 G6.

Primary E.raminer-Benjamin R. Padgett Assistant Examiner-R. E. SchaferAttorney, Agent, or Firm-Mason, Mason & Albright [57] ABSTRACT Thisinvention relates to sintered ferrous materials. Sintered ferrousmaterials in accordance with the invention contain at least 50 percentby weight of iron and glass in an amount of not more than 2 percent byweight. The iron can be present as pure iron or as an alloy thereof. Thematerials can be produced by known powder metallurgical methods, forexample by compression in the presence of a lubricant and subsequentheating. The glass generally serves to seal the pores between theparticles of the iron-containing powder, and the materials have beenfound to have low porosity to gases and liquids and increased corrosionresistance compared with similar materials containing no glass. Sinteredferrous materials in accordance with the invention can be used forproducing valve seats.

11* Claims, No Drawings SINTERED GLASS CONTAINING FERROUS MATERIAL Thisinvention relates to sintered ferrous materials.

According to the invention there is provided a sintered ferrous materialmade by powder metallurgy, the material including iron in an amount ofat least 50 percent by weight and not more than 2 percent by weight ofglass.

Further according to the invention there is provided a process for theproduction ofa sintered ferrous material by powder metallurgy whichincludes sintering a mixture of a powder consisting of at least 50percent by weight of iron and not more than 2 percent by weight of glasspowder.

Sintered ferrous materials in accordance with the invention contain atleast 50 percent by weight of iron. If desired, the materials canconsist on only iron and not more than 2 percent by weight of glass.However, the iron can be present as an alloy. Typical alloys which maybe used include low carbon steels and low alloy steels.

By low carbon steels" we mean alloys of iron and from 0.05 to 0.3percent by weight of carbon, with or without other alloying elements.

By low alloy steels we mean alloys of iron and small quantities ofalloying elements such as nickel, molybdenum or copper, withsubstantially no carbon.

The sintered ferrous materials may contain one or more elements whichare not homogeneous with the iron. Such elements, which may also bealloyed with the iron, include, for example, copper and molybdenum. Ingeneral, the iron will be alloyed and homogeneous with nickel or carbon.

The particle size of the iron-containing powder used to produce sinteredferrous materials in accordance with the invention may be of a valueconventionally used in the powder metallurgical art. Preferably theparticle size is not more than 100 British Standard Mesh, i.e., not morethan 0.152 mm mesh aperture.

The chemical composition of the glass is generally not critical for thepurposes of the present invention and, for example, soda glass, borateglass, borosilicate glass or lead glass can be used. Typical sodaglasses which can be used contain from 71 to 73 percent by weight of SiOfrom 13 to 16 percent by weight Na O, from 5 to percent by weight CaO,from 2 to 5 percent by weight of MgO, and from 0.5 to 1.5 percent byweight of Al O Typical lead glasses can contain from 30 to 36 percent byweight of PbO, from 10 to 13 percent by weight of K 0 and from 53 to 50percent by weight of SiO Although specific chemical composition rangeshave been set forth, the invention is in no way limited thereto.

in general, the glass should be present in an amount of at least 0.125percent by weight.

known powder metallurgical methods can be used in producing sinteredferrous materials in accordance with the invention. Thus a mixture ofthe powder containing at least 50 percent bu weight of iron and not morethan 2 percent by weight of glass powder will in general be compressed,preferably to the desired shape for the sintered ferrous material, forexample under a pressure above 5 Kg/mm Pressures of up to 100 Kg/mm willusually suffice.

Sintering of the powder mixtrue may, for example, be effected at atemperature of from l,000 to 1,300 C,

preferably at about l,lOO C. As will be appreciated by those skilled inthe art, the time required for sintering will depend upon variousfactors, in particular upon the temperature of sintering. Periods of upto 5 hours are generally sufficient and periods of from 1 to 3 hours arepreferred.

Sintering is preferably effected in a reducing atmosphere, for examplein dissociated ammonia (N 3H or an endothermic gas such as a mixture ofpropane and air which has been partially combusted in the presence of acatalyst.

The powder mixture which is sintered can contain not only theiron-containing powder and glass powder but powders of other metals, forexample of copper and/or molybdenum. Furthermore, materials which areconventionally used in the powder metallurgical art can also be added tothe powder mixture prior to sintering. For example, lubricants which aidcompressing of the powder mixture can be added. Suitable lubricantsinclude, for example, zinc stearate, Acrawax (an organic stearate) andgraphite. When graphite is used, it can act not only as a lubricant incompressing the powder mixture but as a source of carbon in the sinteredmaterials. If desired, other forms of carbon than graphite can be addedto the powder mixture for the purposes of increasing the carbon contentof the sintered materials.

After production of sintered ferrous materials in accordance with theinvention, they may, if desired, be subjected to one or moreconventional metallurgical treatment steps, for example case hardeningand tempering or quench hardening and tempering. The case hardening maybe a carburizing or a nitriding process. Tempering can be effected underknown conditions, for example at a temperature of about 175C, preferablyfor a period of about an hour.

The glass in the sintered ferous materials in accordance with theinvention generally serves to reduce the porosity of the materials whencompared with similar materials not containing glass, while generallyretaining the good mechanical strength of sintered ferrous materials notcontaining glass. The reduced porosity has been found of value inapplications where the sintered materials are required to have lowpermeability of liquids or gases. Furthermore, the low porosity canenable case hardening ofthe materials to be effected, attempts to caseharden similar sintered materials containing no glass usually resultingin unsatisfactory products which have been hardened throughout.

Sintered ferrous materials in accordance with the invention have beenfound particularly useful in producing valve seats for use in corrosivemedia where pressure tightness of the valve is important.

The following Examples are given by way of illustration only. All partsare by weight unless otherwise stated and all powdered materials had aparticle size small enough to pass through a No. British Standard Mesh.

EXAMPLE 1 0.25 percent of glass powder was mixed throughly with 99percent of a pre-alloyed stainless iron powder of composition 12 percentchromium and 88 percent iron, and 0.75 percent of Acrawax as alubricant. The mixture was processed by pressing at 63 Kg/mm andsintered at 1100C in dissociated ammonia having a dew point of 35C.

EXAMPLE 2 0.25 percent of powdered glass was thoroughly mixed with 98.8percent of a powdered alloy consisting of I75 percent Ni and 0.5 percentM0, the remainder being Fe (pre-alloyed powder), 02 percent of Bavariangraphite and 0.75 prcent of zinc stearate as a lubricant.

The mixture was processed by pressing at 63 Kg/mm and sintered at l lCin an endothermic gas (produced by partially combusting a propane/airmixture in the presence of a catalyst) having a dew point 4 to 7C. Thiswas followed by a case hardening treatment in a carburizing atmosphere.Finally, tempering was cffected at 175C for 1 hour.

EXAMPLE 3 0.25 percent of powdered glass was thoroughly mixed with 98.6percent ofa powder consisting of 1.75 percent Ni and 0.5 percent Mo theremainder being Fe (pre-alloyed powder), 0.4 percent of Bavariangraphite, and 0.75 percent of zinc stearate.

The mixture was pressed at 63 kg/mm and sintered in an endothermic gas(similar to that used in Example 2) of dew point 7 to l()C at l l00C.The material was then quench hardened from 850C into oil at ambienttemperature and finally tempered at 175C for 1 hour.

EXAMPLE 4 0.25 percent by weight of glass powder was thoroughly mixedwith 4% of copper powder, 0.2 percent of carbon, 0.75 percent of zincstearate as a lubricant, and 94.8 percent of iron powder.

The mixture was pressed at 63 kg/mm and sintered in an endothermic gas(similar to that in Example 2) having a dew point of 0 to 5C, at l l00C.

EXAMPLE 5 0.25 percent by weight of glass powder was thoroughly mixedwith 2 percent of copper, 0.75 percent zinc stearate as a lubricant, and97 percent of iron powder.

The mixture was pressed at tSI'akg/mm and sintered in dissociatedammonia having a maximum dew point of 35C at 1100C.

EXAMPLE 6 0.25 percent by weight of glass powder was thoroughly mixedwith 99 percent of a powdered alloy consisting of l.75 percent Ni and0.5 percent M0, the remainder being iron (pre-alloyed powder) and 0.75percent of zinc stearate as a lubricant.

The mixture was pressed at 79kg/mm and sintered at 1100C in anendothermic gas (similar to that used in Example 2) having a dew pointof l5 to -l7C. This was followed by a case hardening treatment in acarburizing atmosphere. Finally, tempering was effected at l75C for 1hour.

EXAMPLE 7 0.5 percent glass powder was thoroughly mixed with 4 percentof copper, 0.4 percent of carbon, 0.75 percent of zinc stearate as alubricant and 94.35 percent of iron powder. The mixture was pressed at47kg/mm and sintered at ll00C in an endothermic gas (similar to thatused in Example 2) having a dew point of 7to l0C.

EXAMPLE 8 0.25 percent of glass powder was thoroughly mixed with 99percent of a pre-alloyed stainless iron powder containing 12 percent Cr,the remainder being Fe with usual impurities, and 0.75 percent of zincstearate as a lubricant. The mixture was pressed at 71kg/mm and sinteredat ll20C in dissociated ammonia having a dew point of 35C.

EXAMPLE 9 0.25 percent of glass powder was thoroughly mixed with 0.2percent of carbon, 0.75 percent of zinc stearate as a lubricant and 98.8percent of iron powder. The mixture was pressed at 63ltg/mm and sinteredat 1080C in an endothermic gas (similar to that used in Example 2)having a dew point of 0to 5C. This was followed by a case hardeningtreatment in a carbonitriding atmosphere. Finally, tempering waseffected at a temperature of C for l hour.

I claim:

1. A sintered ferrous material made by powder metallurgy, the materialincluding iron in an amount of at least 50 percent by weight and from0.125 to 0.5 percent by weight of glass.

2. A material as claimed in claim l, consisting only of iron and from0.l25 to 0.5 percent by weight of glass.

3. A material as claimed in claim 1, consisting of a ferrous alloy andfrom 0.125 to 0.5 percent by weight of glass, the alloy containing atleast 50 percent by weight of iron.

4. A material as claimed in claim 3, wherein the alloy contains from0.025 to 0.3 percent by weight of carbon.

5. A material as claimed in claim 2, wherein the alloy contains a smallquantity of an alloying element and substantially no carbon.

6. A material as claimed in claim I, in case hardened form.

7. A sintered ferrous material made by powder metallurgy, the materialcomprising stainless iron and from 0.125 to 0.5 percent by weight ofglass.

8. A material as claimed in claim 1 wherein the glass is selected fromthe group consisting of soda glass, borate glass, borosilicate glass,and lead glass.

9. A material as claimed in claim 8, wherein the glass contains from 71to 73 percent by weight SiO from 13 to 16 percent by weight of Na O,from 5 to l0 percent by weight of CaO, from 2 to 5 percent by weight ofMgO and from 0.5 to 1.5 percent by weight Al O 10. A material as claimedin claim 8, wherein the glass'contains from 30 to 36 percent by weightPhD, from 10 to 13 percent by weight K 0 and from 53 to 56 percent byweight SiO 11. A material as claimed in claim 7, in case hardened form.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3.891.399 Dated June 24 197% Inventor(s) Terence M. Cadle It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Page one, the assignee should be corrected from "Bries Engineering Ltd."to Brico Engineering Ltd.

Signcd and Scaled this fourth Day of May 1976 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN Allvsling Officer Commissioner nj'lannlsand Trademarks

1. A SINTERED FERROUS MATERIAL MADE BY POWDER METALLURGY, THE MATERIALINCLUDING IRON IN AN AMOUNT OF AT LEAST 50 PERCENT BY WEIGHT AND FORM0.125 TO 0.5 PERCENT BY WEIGHT OF GLASS.
 2. A material as claimed inclaim 1, consisting only of iron and from 0.125 to 0.5 percent by weightof glass.
 3. A material as claimed in claim 1, consisting of a ferrousalloy and from 0.125 to 0.5 percent by weight of glass, the alloycontaining at least 50 percent by weight of iron.
 4. A material asclaimed in claim 3, wherein the alloy contains from 0.025 to 0.3 percentby weight of carbon.
 5. A material as claimed in claim 2, wherein thealloy contains a small quantity of an alloying element and substantiallyno carbon.
 6. A material as claimed in claim 1, in case hardened form.7. A sintered ferrous material made by powder metallurgy, the materialcomprising stainless iron and from 0.125 to 0.5 percent by weight ofglass.
 8. A material as claimed in claim 1 wherein the glass is selectedfrom the group consisting of soda glass, borate glass, borosilicateglass, and lead glass.
 9. A material as claimed in claim 8, wherein theglass contains from 71 to 73 percent by weight SiO2, from 13 to 16percent by weight of Na2O, from 5 to 10 percent by weight of CaO, from 2to 5 percent by weight of MgO and from 0.5 to 1.5 percent by weightAl2O3.
 10. A material as claimed in claim 8, wherein the glass containsfrom 30 to 36 percent by weight PbO, from 10 to 13 percent by weight K2Oand from 53 to 56 percent by weight SiO2.
 11. A material as claimed inclaim 7, in case hardened form.